<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <style>
        *{
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        body{
            width: 509px;
            margin: auto;
            /* border: 1px solid red; */
            margin-top: 60px;
        }
        button{
            border: 0;
            background-color: transparent;
            cursor: pointer;
        }
        .btn1{
            position: relative;
        }
        .btn1::before{
            content: "";
            border: 1px solid red;
            width: 88px;
            height: 88px;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%) scale(1);
            transition: 0.3s;
            border-radius: 999px;
        }
        .btn1::after{
            content: "";
            border: 1px solid red;
            width: 122px;        /*    唯一不同的地方    */
            height: 122px;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%) scale(1);
            transition: 0.3s;
            border-radius: 999px;
        }

        /* 鼠标放上去的时候:    */
        .btn1:hover::before,
        .btn1:hover::after{
            transform: translate(-50%, -50%) scale(1.3);
        }
    </style>
        <button class="btn1">btn1</button>




        <xmp style="font-size: 22px; font-weight: bolder;  margin-bottom: 66px;  color: black;  font-family: '微软雅黑';">
            
            必知必会
           
            .btn1::before{
                content: "";
                border: 1px solid red;
                width: 88px;
                height: 88px;
                position: absolute;
                top: 50%;
                left: 50%;
                transform: translate(-50%, -50%) scale(1);
                transition: 0.3s;
                border-radius: 999px;
            }

            /* 鼠标放上去的时候:    */
            .btn1:hover::before,
            .btn1:hover::after{
                transform: translate(-50%, -50%) scale(1.3);
            }
        </xmp>












<hr  style="margin:   5px 0 ;">








        <style>
            .btn2{
                margin-top: 123px;
                background: lightsteelblue;
                padding: 12px  123px;
                position: relative;
                font-size: 35px;
            }
            .btn2::before{
                content: "<<";
                position: absolute;
                left: 10px;
                transition: 0.3s;
                opacity: 0;
            }
            .btn2::after{
                content: ">>";
                position: absolute;
                right: 50px ;
                transition: 0.3s;
                opacity: 0;
            }
            .btn2:hover:after{
                transform: translateX(50%);
                opacity: 1;
            }
        </style>
        <button class="btn2">btn2</button>


        <xmp style="font-size: 22px; font-weight: bolder;  margin-bottom: 66px;  color: black;  font-family: '微软雅黑';">
            .btn2::after{
                content: ">>";
                position: absolute;
                right: 50px ;
                transition: 0.3s;
                opacity: 0;
            }
            .btn2:hover:after{
                transform: translateX(50%);
                opacity: 1;
            }
        </xmp>



</body>
</html>